1. Field of the Invention
The present invention relates to a filler pipe for feeding the fuel from a fuel inlet to a fuel tank in an automobile.
2. Description of Related Art
A filler pipe is used in an automobile for feeding the fuel from a fuel inlet to a fuel tank. Such a filler pipe is combined with a breather pipe, which functions for venting the space above a liquid level in the fuel tank and is provided with a bracket for fixing the filler pipe together with the breather pipe with a vehicle body. Conventionally, such a filler pipe is made from a steel material, in which a painting or plating is necessary as a countermeasure to the problem of corrosion. Recently, from a viewpoint of reduction of weight, a filler pipe made of a stainless steel has been proposed. In a well-known manner, the stainless steel forms, on its outer surface, a passive layer of an increased corrosion resistance, by which a surface coating by a painting or plating becomes basically unnecessary. However, the stainless steel is accompanied with a problem of so-called crevice corrosion. The crevice corrosion is a phenomenon where a contact of a water with a crevice causes an electric potential difference to be created between the portion of the crevice of a low oxygen density and an out side portion of a high oxygen density, thereby creating a so-called corrosion battery as a kind of an oxygen concentration cell. In the corrosion battery, the crevice becomes as an anode, whereat corrosion is likely generated. The filler pipe is provided with a bracket for allowing the filler pipe to be fixed with the vehicle body. In the case where a fixture of such a bracket is done by a welding, the welding along the entire periphery of the mating surfaces between the filler pipe and the bracket is actually difficult, which would otherwise increase the labor cost unreasonably. Thus, to some extent, gaps are inevitably created at the welded portion, whereat corrosion is likely generated. As a measure to the crevice corrosion as occurred by welding, a coating with a paint is usually employed and a cation electrodeposition coating popular is suitable in view that a strong coated film is obtained at a low cost. U.S. Pat. No. 6,615,498 (Japanese Un-Examined Patent Publication No. 2002-242779) discloses a cation electrodeposition coating to a filler pipe made of stainless steel.
In the prior art, a usual teaching for combating corrosion is a coating by paint. Namely, an application of paint is done in such a manner that the coated film covers a gap between the welded surfaces by the paint. However, the coating by the paint usually accompany with problems that a thickness of the coated film is varied and a flow of the paint is not enough to completely fill the gap, so that a possibility of a generation of the crevice corrosion is still left.
In order to completely prevent the crevice corrosion from being occurred, a two-piece structure is proposed, wherein the filler pipe and the bracket are coated with the cation paint separately, which is followed by a bolt connection of the bracket to the filler pipe. In this case, a space between the filler pipe and the bracket is completely filled by the coated film, so that any crevice corrosion does not occur. However, due to the resultant increase in the total number of parts, a cost is increased over that of the one-piece structure.